I have been using the Skywatch system produced by B.F.Goodrich in my Saratoga. It was bloody expensive but my wife thinks it's wonderful.
BUT it's not the whole story. You only get warnings of transponding A/C and only up to 6 miles range. However as I am based at Blackbushe in some of the busiest skies in the UK I consider it to be a sound investment. Strangely, since I had the kit fitted, I look out the window more than ever.